Thalassoleon=Megalotaria?

Darren Naish recently posted on this form and the message elicited a response from Jay Cooney that this could be the fossil form of Heuvelmans' "Megalotaria" (he expressed displeasure in bringing the subject up) I agreed that if ever a fossil species deserved that name, then Thalassoleon macnallyae at the size of a walrus would deserve that name.

Thalassoleon

http://en.wikipedia.org/wiki/Thalassoleon

Thalassoleon is an extinct genus of large fur seal. Thalassoleon inhabited the Northern Pacific ocean in latest Miocene and early Pliocene time. Fossils of T. mexicanus are known from Baja California and southern California. T. macnallyae is known from central California, and T. inouei (which may be a synonym of T. macnallyae) is known from Japan.Thalassoleon could be the ancestor of the modern Northern Fur Seal.

T. mexicanus was comparible in size to the largest fur seals, with an estimated weight of 650-700 lbs.^[1] T. macnallyae, based on size of the mandible, may have grown much larger, similar in size to a walrus.

References

1. Jump up^ Geological Survey professional paper, Volume 992 By Geological Survey (U.S.)

https://www.sdnhm.org/archive/research/paleontology/DemereBerta-lrThal-05.pdf

Incidentally the female was 50% the size of the male which is close to modern fur seals. Fossils are found in the North Pacific, from Baja California to Mexico.

FossilWorks gives this data on the largest species:
http://fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=72014


Thalassoleon macnallyae Repenning and Tedford 1977 (eared seal)

Mammalia - Theriiformes - Otariidae

Full reference: C. A. Repenning and R. H. Tedford. 1977. Otarioid seals of the Neogene. Geological Survey Professional Paper 992:1-93

Belongs to Thalassoleon according to T. A. Demere and A. Berta 2005

See also Barnes 1989, Barnes 2008, Demere et al. 2003 and Repenning and Tedford 1977

Sister taxa: Thalassoleon inouei, Thalassoleon mexicanus

Type specimen: UCMP 112809, a partial skull. Its type locality is Drakes Beach, which is in a Messinian marine sandstone in the Drakes Bay Formation of California.

Ecology: amphibious piscivore

Age range: 7.246 to 5.332 Ma

Distribution: found only at Drakes Beach

And this on the more usual-sized species:

http://fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=72013

†Thalassoleon mexicanus Repenning and Tedford 1977 (eared seal)

Mammalia - Theriiformes - Otariidae

Full reference: C. A. Repenning and R. H. Tedford. 1977. Otarioid seals of the Neogene. Geological Survey Professional Paper 992:1-93

Belongs to Thalassoleon according to T. A. Demere and A. Berta 2005

See also Barnes 1989, Barnes 2008, Demere et al. 2003, Repenning and Tedford 1977 and Vidal 1991

Sister taxa: Thalassoleon inouei, Thalassoleon macnallyae

Type specimen: IGCU 902, a skull

Ecology: amphibious piscivore
Environments: coastal (all collections)

Age range: 7.246 to 3.6 Ma

Distribution:

• Pliocene of Japan (1 collection), United States (1: California)

• Miocene of Mexico (1), United States (1: California)

Total: 4 collections each including a single occurrence

"thalassoleon_by_hodarinundu-d4pu5g8" above, a probably not very accurate reconstruction from Deviant Art.   "Thalassoleon_mexicanusingame1"  below

Admittedly the fossils are very sparse and there is only one specimen for the larger species. However it is just possible that the larger species (or one derived from it) could have survived the ice age, be alive today as the "Megotaria" (in sealion form, as we have construed it) and might have worked its way around to including also a North Atlantic population. So at this point I would like to declare that the best possibility we have suggested so far is that "Megalotaria" is only the continuing survival of the large species of Thalassoleon. That assumption could easily prove wrong for any number of reasons. But it is still the best suggestion that we have to go on at the present time.